1. Field of the Invention
The present invention relates to the remote control of electric power actuated apparatuses and more particularly to electric circuit switching devices.
This invention can be used in devices for controlling a group of electric power actuated apparatuses, for instance, a group of electric motors, in various branches of industry, particularly in coal mining.
2. Description of the Prior Art
Known in the art are devices for controlling a group of electric motors (control stations) comprising a plurality of contactors, intermidiate electromagnetic relays and other switching elements, the number of which depends on the number of electric motors to be controlled. Such devices are complicated in construction, bulky and not very reliable in operation.
Furthermore, the designing of devices for controlling machines operated in mines with a dangerously explosive atmosphere offers special difficulties since insuring the safety of operation in such mines requires meeting a number of specific safety requirements such as, for instance, testing of insulation of the electric circuits connecting production equipment with power sources. Such testing is carried out before each of the above electric circuits is connected to the sources of electric power. In order to meet these requirements, it is necessary that special control means be included in each set of devices, intended for controlling only one electric power actuated apparatus.
Also known in the art is a high voltage circuit switching device (c.f. USSR Inventor's Certificate No. 320,846) comprising a group of closing contact pairs and a group of breaking contact pairs, each of the pairs having stationary contacts arranged circumferentially on the insulating panel, and a switching element. In addition, the switching device includes a unit for rotating the switching elements and an electromagnetic drive providing translatory motion of the switching elements while closing and breaking contacts. The electromagnetic drive in said switching device is a solenoid, the armature of which has switching elements on its opposite ends. Each of the switching elements is a disk made of an insulating material and has a pair of electrically connected contacts. The armature of the solenoid moves between parallel insulating panels, each of the panels carrying said stationary contacts being arranged perpendicular to the direction of its movement. Rotation of the armature of the solenoid about its axis and, consequently, of the switching elements through a pre-set angle is effected by a unit comprising a cam mounted on the armature of the solenoid. On the cylindrical surface of the cam there is a saw-like groove, while on the body of the solenoid is mounted a spring-loaded pin set into said saw-like groove.
The above switching device makes it possible to alternately close and break the contacts arranged beside each other, but does not provide for selective switching thereof. In addition, the aforedescribed switching device does not ensure the protection of the electric power actuated apparatuses in case of zero voltage in the feed line. Thus, to provide reliable control of a group of electric power actuated apparatuses apart from the above switching device, various additional elements and means, such as relays, are required, which makes the electric circuit of the controlling device more complicated.
It should be pointed out that the increase in the number of electric power actuated apparatuses leads to an enlargement of the switching device dimensions and to more complicated electric connections.
It is also worthwhile pointing out that said switching device does not permit closing each of those contacts regardless of breaking the others.